Ch. 23 Urinary System

Efferent Arteriole

arteriole that carries concentrated blood (more cells, less plasma) away from glomerulus to peritubular capillaries. -Smaller in diameter as compared to afferent arterioles.

Proximal Convoluted Tubule

cuboidal cells w/numerous microvilli and mitochondria; reabsorbs water and solutes from filtrate and secretes substances into it the Loop of Henle - Confined entirely to the renal cortex

Vasa Recta

hairpin looping vessels that descend into medulla,running alongside loops of Henle.

Collecting Duct System

receive urine from several nephrons and runs straight through the cortex into medulla. - Concentrates urine...ADH hormone increases permeability of the collecting tubules and distal tubules to water. -At apex of pyramid, adjacent collecting tubules join to form larger papillary ducts that become minor calices

Urinary bladder

smooth, collapsible, muscular sac that temporarily stores urine. Up to 1 liter

Urinary System

specifically the kidneys maintain the purity and chemical constancy of the blood and other extracellular body fluids.

Paired ureters

tube-like structure (MUSCULAR duct)that actively transports urine from kidneys to bladder via response to smooth muscle stretch -continuation of the renal pelvis. -The distal ends close in response to any increase of pressure w/in bladder to prevent backflow of urine.

Urethra

tube-like structure that transports urine from the bladder out of the body • Note: Has an excretory function in both sexes to pass urine, and also a reproductive function in the male, as a passage for semen.

Ureters: Microscopic Anatomy

a) Mucosa: transitional epithelium and lamina propria composed of stretchy, fibroelastic C.T. b) Muscularis: inner longitudinal layer and an outer circular layer of smooth muscle. c) Adventitia: external wall made up of a typical C.T.

Renal Corpuscle

first part of nephron, strictly in cortex. -Consists of bunch of capillaries called glomerulus plus a glomerular capsule (Bowman's capsule). -The purpose of renal corpuscle is extract renal filtrate (not yet to be called urine) from blood. -glomerular endothelium is fenestrated allowing large quantities of fluid and small molecules to pass from the capillary blood into the hollow interior of the glomerular capsule...the capsular space.

Renal Pelvis

flat, funnel-shaped expansion of the ureter. - Branching extensions of the renal pelvis form two or three major calices, each of which divides to minor calices, cupshaped tubes that enclose the papillae of the pyramids.

Afferent Arteriole

group of blood vessels that supply nephrons in many excretory systems. -branch from renal artery and feed glomerular capillaries. -Larger in diameter than efferent arterioles.

Trigone

triangular region on posterior wall outlined by openings for the ureters and urethra -Clinically important because infections tend to persist in this region

Renal Hillus

vertical cleft located on medial surface where renal blood vessels, ureters, lymphatics and nerves enter and leave the kidney.

Kidneys: Layers

1) Cortex: The superficial cortex region is light in color and has a granular appearance. 2) Medulla: Deep to the cortex is the darker renal medulla, which consists of cone-shaped masses called medullary pyramids/renal pyramids. -broad base of each pyramid abuts the cortex whereas the pyramid's apex (papilla) points internally. -The renal columns, inward extensions of the renal cortex, separate adjacent pyramids.

Bowman's Capsule (aka Glomerular Capsule):

-contains the glomerulus (capillary network). -The inner layer is very porous to extract and absorb plasma from glomerulus. -outer layer impermeable to contain the plasma that has been extracted

Urethra regions

Males: the urethra is about 8 inches and three named regions: - Prostatic urethra: 2.5 cm long and runs in the prostate gland - Membranous urethra: 2.5 cm long and runs through the urogenital diaphragm - Spongy (Penile) urethra: 15 cm long, passes through the entire penis. and opens at the tip of the penis via the external urethral orifice

Classes of Nephrons

Nephrons are divided into 2 categories based on location: 1) Cortical nephrons: 85% of nephrons; located in the cortex (except for part of Loop of Henle in medulla) 2) Juxtamedullary nephrons: 15% are located at the cortex-medulla junction, loops of Henle that deeply invade medulla, have extensive thin segments, are involved in the production of concentrated urine

Flow of urine

Renal papillae→Minor calyx→Major calyx→Renal pelvis→Ureter→Bladder→Urethra→Outside of body

Kidneys: External Gross Anatomy

Several layers of supportive tissue surround each kidney... 1) Renal capsule: A thin layer of dense C.T. adheres directly to the kidney's surface...maintaining its shape and forming a barrier that can inhibit the spread of infection from the surrounding regions. 2) Adipose capsule: Consists of perirenal fat. just external to that is an envelope of renal fascia. 3) Pararenal fat: Lies external and mostly posterior to the renal fascia. -The perirenal and pararenal fat layers function to cushion the kidney against blows an help hold kidney in place.

Urethra Sphincters

Sphincters keep urethra closed when urine is not being passed: a) Internal urethral sphincter: involuntary sphincter at bladderurethral junction b) External urethral sphincter: voluntary sphincter surrounding urethra as it passes through the urogenital diaphragm c) Levator ani muscle: voluntary urethral sphincter

Urinary Bladder: Microscopic Anatomy

a) Mucosa: transitional epithelium an lamina propria b) Muscular layer: thick detrusor muscle; consist of smooth muscle fibers arranged in inner and outer longitudinal layers and a middle circular layer...Contraction squeezes urine from the bladder during urination. c) Adventitia: fibrous C.T. • bladder is distensible an collapses when empty • As urine accumulates, the bladder expands without significant rise in internal pressure

Renal Tubule

a) proximal convoluted tubule, b) loop of Henle, c) distal convoluted tubule and d) collecting tubule.

Nephron

basic structural and functional unit of the kidney. -chief function is regulate concentration of water and soluble substances like sodium salts by filtering the blood, reabsorbing whats needed and excreting the rest as urine.

Distal Convoluted Tubule

cuboidal cells w/out microvilli that function more in secretion than reabsorption - Confined to the renal cortex.

Renal Sinus

large "filled space" within the medial part of the kidney opening to the exterior through the renal hilus. -Contains the renal vessels and nerves, some fat, and the urine carrying tubes called the renal calices and renal pelvis

Kidneys: Overview location

lie "retroperitoneal" (behind the parietal peritoneum), extend from T11-12 to the L3. Right kidney slightly inferior to the left kidney; has 5-11 lobes...each of which is a single renal pyramid plus the cortical tissue that surrounds that pyramid.

Uriniferous tubules

main structural and functional unit of the kidney. They are composed of: 1) A urine-forming nephron consisting of...Renal corpuscle, proximal convoluted tubule, loop of Henle, and distal convoluted tubule 2) A collecting duct: involved in concentrating urine by removing water from it. • lined by a simple epithelium.

Kidney: function

- The kidneys filter many liters of fluid from the blood, sending toxins, metabolic wastes, excess water, and excess ions out of the body in urine while returning needed substances back to the blood. - Three main wastes products: 1) Urea 2) Uric acid 3) Creatine • The kidneys also regulate the volume and chemical makeup of the blood

Peritubular Capillaries

network of low pressure and porous capillaries that surround interstitial C.T. of renal cortex, clinging closely to convoluted tubules and empty into nearby venules. -Function: reabsorb some of the nutrients and plasma that were extracted in the Bowman's capsule.

Loop of Henle

portion of the nephron that leads from the proximal convoluted tubule to the distal convoluted tubule. loop in renal medulla. - reabsorb water and ions from the urine.

Uriniferous tubules produce urine though three interacting mechanisms???

1) Filtration: filtrate of the blood leaves the kidney capillaries and enters the nephron. 2) Reabsorption: most nutrients, water, and essential ions are recovered from filtrate and returned to the blood of capillaries in surrounding CT. 3) Secretion: remaining wastes contribute to the urine that leaves the body.